Failure at the femoral stem extension-condylar interface in a rotating hinge knee without radiographic evidence of loosening.

Modular stem extensions have become ubiquitous in revision total knee arthroplasty systems. Although stem extensions are valuable in addressing bone deficiencies and improving implant fixation, the stem extension-condylar interface may be a point of implant failure. We report a case of failure at the femoral stem extension-condylar interface in a Zimmer NexGen Rotating Hinge Knee (Zimmer, Warsaw, IN). Currently, several published case reports describe failure at the femoral stem extension-condylar interface but only 1 case describes loosening at a taper junction without evidence of set screw failure or taper fracture. Furthermore, no published cases describe this type of failure in the Zimmer NexGen Rotating Hinge Knee (Zimmer).